This invention relates to a method for applying an electrostatic coating on a resin molding.
As conventional methods for electrostatically coating a resin molding, there are included such as a method described in Japanese Laid-Open Patent Publication No. 66,538 of 1975 in which a conductive paint containing conductive metal powder is applied on the surface of a resin molding to form a conductive primer layer and then an electrostatic coating is performed, and a method in which an inorganic conductive substance such as carbon black, carbon fiber or conductive mica is mixed with the resin and the mixture is molded and then the molding is electrostatically coated.
However, these conventional methods for electrostatically coating a resin molding have the following disadvantages to cause difficulty in their practical uses.
For example, in the case of which a conductive primer layer is formed on the surface of a resin molding as described in Japanese Laid-Open Patent Publication No. 66,538 of 1975, the adhesion between the surface of the resin molding and the conductive primer applied on it is poor. To improve the adhesion, a multilayer of various conductive primer layers shall be necessarily formed. It causes not only difficulties in conductivity and productivity but also problems in the application loss and its cost due to the use of various types of conductive primer.
In the case of which an electrostatic coating is applied to a resin molding comprising a conductive substance such as carbon black, carbon fiber or conductive mica, the conductive substance shall be inevitably mixed with the resin in a large amount. Thus, it tends to cause the deterioration of the resin molding and affects the color of the surface of electrostatic coating by coloring the resin molding.
The object of the present invention is to provide a method of applying an electrostatic coating excellent in applicability and adhesion on a resin molding with no substantial deterioration in phyical properties and color of the resin.